Micromachine and Method for Manufacturing the Same

ABSTRACT

A structure which prevents thinning and disconnection of a wiring is provided, in a micromachine (MEMS structure body) formed with a surface micromachining technology. A wiring (upper auxiliary wiring) over a sacrificial layer is electrically connected to a different wiring (upper connection wiring) over the sacrificial layer, so that thinning, disconnection, and the like of the wiring formed over the sacrificial layer at a step portion generated due to the thickness of the sacrificial layer can be prevented. The wiring over the sacrificial layer is formed of the same conductive film as an upper driving electrode which is a movable electrode and is thus thin. However, the different wiring is formed over a structural layer, which is formed by a CVD method and has a rounded step, and has a thickness of 200 nm to 1 μm, whereby thinning, disconnection, and the like of the wiring can be further prevented.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a structure of a micromachine which isformed with a microelectromechanical system (MEMS) technology.

2. Description of the Related Art

These days, MEMS switches which utilize a MEMS technology, and sensors,resonators, communication devices, and the like which are provided withthe MEMS switches have been attracting attention.

These are also called micromachines, and there are two kinds oftechnologies, a surface micromachining technology and a bulkmicromachining technology, depending on manufacturing methods. In thesurface micromachining technology, thin films are stacked over asubstrate and then processed by a photolithography method or an etchingmethod, whereby a MEMS structure body can be formed. Further, in thebulk micromachining technology, a silicon wafer or a silicon oninsulator (SOI) substrate itself is processed by etching or polishing,whereby a MEMS structure body can be formed.

In particular, great importance is placed on the surface micromachiningtechnology because a semiconductor process can be applied thereto.However, through the surface micromachining technology, a MEMS structurebody has a three-dimensional structure in which thin films are stacked,and thus, a connection wiring which is formed at a step portiongenerated due to a thick layer (for example, a sacrificial layer) iseasily thinned or disconnected; therefore, there is a problem in thatthe reliability of the wiring is significantly lowered.

Therefore, a method is proposed by which, in the case that a wiring isformed at a step portion generated due to a thick layer, the thick filmis easily tapered with a given angle and the taper angle can more easilybe controlled (for example, see Reference 1: Japanese Published PatentApplication No. H7-66280).

SUMMARY OF THE INVENTION

However, in the MEMS structure body, because the sacrificial layer isvery thick, it is difficult to control a process to achieve formation ofa desired taper shape in the sacrificial layer so that thinning anddisconnection of the wiring can be prevented.

In view of the foregoing problems, it is an object of the presentinvention to provide a structure which prevents thinning anddisconnection of a wiring at a step portion of a sacrificial layer, in amicromachine (MEMS structure body) which is formed with the surfacemicromachining technology.

In order to solve the foregoing problems, in the present invention,wirings (upper auxiliary wirings) are formed over a sacrificial layer byusing the same conductive film and in the same plane as those of upperdriving electrodes and are electrically connected to different wirings(upper connection wirings) whose thickness can be relatively freelydetermined, over the sacrificial layer. Further, a step portiongenerated due to the thickness of the sacrificial layer is rounded by astructural layer which is formed over the sacrificial layer using a filmobtained by a CVD method, and the different wirings are formed over thestructural layer.

Further, in the present invention, the structural layer is formed overthe entire surface where films are formed (that is, the structural layeris formed to cover underlying films), so that all the different wirings(the upper connection wirings) can be formed over the structural layer.

Specifically, according to an aspect of the present invention, amicromachine includes a first electrode over a substrate having aninsulating surface, a second electrode and an auxiliary wiring over thefirst electrode with a space interposed therebetween, and a connectionwiring over the auxiliary wiring. In this structure, the secondelectrode, the auxiliary wiring, and the connection wiring areelectrically connected to one another; the first electrode is a fixedelectrode; the second electrode is a movable electrode; the secondelectrode and the auxiliary wiring are formed in the same plane; and theauxiliary wiring and the connection wiring are electrically connected toeach other over the space.

Further, according to another aspect, a micromachine includes a firstelectrode over a substrate having an insulating surface, a secondelectrode and an auxiliary wiring over the first electrode with a spaceinterposed therebetween, a structural layer over the second electrodeand the auxiliary wiring, and a connection wiring over the structurallayer. In this structure, the first electrode is a fixed electrode; thesecond electrode is a movable electrode; the second electrode and theauxiliary wiring are formed in the same plane and electrically connectedto each other; and the auxiliary wiring and the connection wiring areelectrically connected to each other through an opening which isprovided in the structural layer.

In the above structure, the structural layer is formed using a filmwhich is formed by a CVD method.

In the above structure, the thickness of the connection wiring is 200 nmto 1 μm, preferably 300 to 600 nm.

In the above structure, the connection wiring is formed of a metalmaterial such as tantalum (Ta), aluminum (Al), titanium (Ti), molybdenum(Mo), tungsten (W), gold (Au), or platinum (Pt), or metal oxide or metalnitride of the metal material.

Furthermore, according to another aspect of the present invention, amethod for manufacturing a micromachine includes the following steps:forming a first electrode over a substrate having an insulating surface,forming a sacrificial layer over the first electrode, forming a secondelectrode and an auxiliary wiring which are electrically connected toeach other over the sacrificial layer, forming a structural layer overthe second electrode and the auxiliary wiring, forming a first openingin the structural layer in a position overlapping with the auxiliarywiring, forming a connection wiring over the structural layer to beelectrically connected to the auxiliary wiring through the firstopening, forming a second opening in the structural layer in a positionoverlapping with the sacrificial layer, and removing the sacrificiallayer by etching using the second opening.

In the above method, the structural layer is formed by a CVD method.

According to the present invention, in a micromachine (MEMS structurebody) which is formed with a surface micromachining technology, a wiring(an upper auxiliary wiring) formed over a sacrificial layer iselectrically connected to a different wiring (an upper connectionwiring) over the sacrificial layer. Thus, thinning, disconnection, andthe like of the wiring formed over the sacrificial layer at a stepportion generated due to the thickness of the sacrificial layer can beprevented, whereby a highly reliable micromachine can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a structure of a MEMS switch according to an aspectof the present invention.

FIGS. 2A to 2D illustrate a method for manufacturing a MEMS switchaccording to an aspect of the present invention.

FIGS. 3A to 3D illustrate a method for manufacturing a MEMS switchaccording to an aspect of the present invention.

FIGS. 4A to 4D illustrate a method for manufacturing a MEMS switchaccording to an aspect of the present invention.

FIGS. 5A to 5E illustrate a method for manufacturing a MEMS switchaccording to an aspect of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, an embodiment mode of the present invention will bedescribed in detail with reference to the drawings. Note that thepresent invention is not limited to the following description, and modesand details thereof can be modified in various ways without departingfrom the spirit and the scope of the present invention. Therefore, thepresent invention should not be construed as being limited to thefollowing description of the embodiment mode.

Embodiment Mode 1

In Embodiment Mode 1, a structure of a microelectromechanical system(MEMS) switch which is a micromachine according to the present inventionwill be described.

As illustrated in FIG. 1, in a MEMS switch, lower driving electrodes102, a lower switch electrode 103, and lower auxiliary wirings 104 areprovided over a substrate 101 having an insulating surface. Further,upper driving electrodes 106, an upper switch electrode 107, and upperauxiliary wirings 108 are provided over the lower driving electrodes102, the lower switch electrode 103, and the lower auxiliary wirings 104with a space 105 interposed therebetween. The upper driving electrodes106, the upper switch electrode 107, and the upper auxiliary wirings 108are formed to be integrated with a structural layer 109. In FIG. 1, across section of the structural layer 109 is partly illustrated by adashed line 112 to make the description more detailed, but thestructural layer 109 actually covers an upper part of the space 105.

The lower driving electrode 102 serves as a fixed electrode which isformed over the substrate 101. On the other hand, the upper drivingelectrode 106 serves as a movable electrode which is arranged to facethe lower driving electrode 102 and operates by electrostatic attractionor electrostatic repulsion generated in the space 105 between the upperdriving electrode 106 and the lower driving electrode 102. That is, inthe case that the upper driving electrode 106 is attracted to the lowerdriving electrode 102, the lower switch electrode 103 and the upperswitch electrode 107 are in contact with each other and electricallyconnected to each other; whereas in the case that the upper drivingelectrode 106 and the lower driving electrode 102 repel each other, thelower switch electrode 103 and the upper switch electrode 107 areseparated and electrical connection is terminated.

The MEMS switch illustrated in FIG. 1 has a post-and-beam structure inwhich either end of the structural layer 109 is fixed to the substrate101, but the present invention is not limited thereto, and a cantileverstructure in which only one end of the structural layer 109 is fixed tothe substrate 101 may also be employed. In addition, here, one lowerswitch electrode 103 and one upper switch electrode 107 are formed,whereas two lower driving electrodes 102 and two upper drivingelectrodes 106 are formed. However, one lower driving electrode 102 andone upper driving electrode 106 may be formed, or three or more lowerdriving electrodes 102 and three or more upper driving electrodes 106may be formed.

The lower driving electrode 102 is electrically connected to a lowerconnection wiring 110 through the lower auxiliary wiring 104 which isformed in the same plane as the lower driving electrode 102.

The upper driving electrode 106 is electrically connected to an upperconnection wiring 111 through the upper auxiliary wiring 108 which isformed in the same plane as the upper driving electrode 106. In thepresent invention, the upper connection wiring 111 is formed over thestructural layer 109 and electrically connected to the upper auxiliarywiring 108 which is formed in the same plane as the upper drivingelectrode 106, through an opening formed in the structural layer 109 ina position overlapping with the upper auxiliary wiring 108.

Therefore, by applying voltage between the lower connection wiring 110and the upper connection wiring 111, electrostatic attraction isgenerated between the lower driving electrode 102 and the upper drivingelectrode 106, whereby the upper driving electrode 106 which is amovable electrode can operate.

Next, a method for manufacturing a MEMS switch having the abovestructure will be described with reference to FIGS. 2A to 2D, FIGS. 3Ato 3D, FIGS. 4A to 4D, and FIGS. 5A to 5E.

First, as illustrated in FIGS. 2A and 2B, lower driving electrodes 202,a lower switch electrode 203, and lower auxiliary wirings 204 are formedover a substrate 201. FIG. 2A is a top view illustrating part of theMEMS switch illustrated in FIG. 1, and FIG. 2B is a cross-sectional viewtaken along line A-A′ in the top view of FIG. 2A.

The substrate 201 can be a glass substrate, a quartz substrate, aplastic substrate, or the like having an insulating surface.Alternatively, a conductive substrate such as a metal substrate or asemiconductor substrate such as a silicon substrate, over which aninsulating film is formed, can be used.

The lower driving electrodes 202, the lower switch electrode 203, andthe lower auxiliary wirings 204 are formed by pattering the sameconductive film into desired shapes. Here, as the conductive film, forexample, a metal material such as tantalum (Ta), aluminum (Al), titanium(Ti), molybdenum (Mo), tungsten (W), gold (Au), or platinum (Pt), acompound (metal oxide or metal nitride) of the metal material, or thelike can be used. The thickness of the conductive film is preferably 50to 700 nm, more preferably 100 to 300 nm. Note that a material is neededto be selected which is not etched at the time of etching a sacrificiallayer that is formed in the next step.

In patterning the conductive film, a method is employed in which aresist mask is formed by a photolithography method and then theconductive film is partly removed by an etching method. As an etchingmethod, a dry etching method or a wet etching method can be used. In adry etching method, an etching gas including CHF₃, ClF₃, NH₃, CF₄, orthe like can be used. Further, in a wet etching method, an etchantincluding a hydrogen peroxide solution or an etchant including bufferedhydrofluoric acid can be used.

Next, as illustrated in FIGS. 2C and 2D, a sacrificial layer 205 isformed with a desired shape over the substrate 201 so as to cover thelower driving electrodes 202 and a part of the lower switch electrode203. FIG. 2D is a cross-sectional view taken along line A-A′ in a topview of FIG. 2C.

The sacrificial layer 205 is formed to provide a space in part of theMEMS switch later. Therefore, the sacrificial layer 205 is eventuallyremoved by an etching method or the like, so that either a conductivematerial or an insulating material can be used for the sacrificial layer205. Note that, as described above, the sacrificial layer 205 is neededto be formed by selecting a material with a higher etching rate than theconductive material used for the lower driving electrodes 202, the lowerswitch electrode 203, and the lower auxiliary wirings 204, and further,with a higher etching rate than a conductive material used for upperdriving electrodes, an upper switch electrode, upper auxiliary wirings,and auxiliary electrodes which are formed later.

In the case of using a conductive material for forming the sacrificiallayer 205, a metal material such as tungsten (W) or molybdenum (Mo) canbe used. In the case of using an insulating material for forming thesacrificial layer 205, a material which can be easily removed by etchingis preferably used such that electrical connection between the switchelectrodes (the lower switch electrode and the upper switch electrode)of the MEMS switch is not adversely affected. Specific examples of sucha material include a resin material such as an acrylic resin, a phenolresin, a novolac resin, a melamine resin, or an urethane resin; anorganic material such as benzocyclobutene, polyamide, polyimide, orresist; an inorganic material such as silicon; and the like.

The thickness of the sacrificial layer 205 is preferably 1 to 5 μm, morepreferably 2 to 3 μm.

Then, as illustrated in FIGS. 3A and 3B, upper driving electrodes 206,an upper switch electrode 207, and upper auxiliary wirings 208 areformed with desired shapes over the sacrificial layer 205. In addition,auxiliary electrodes 209 are formed with desired shapes over the lowerauxiliary wirings 204. FIG. 3B is a cross-sectional view taken alongline A-A′ in a top view of FIG. 3A.

The upper driving electrodes 206, the upper switch electrode 207, theupper auxiliary wirings 208, and the auxiliary electrodes 209 are formedby pattering the same conductive film into desired shapes. Here, as theconductive film, for example, a metal material such as tantalum (Ta),aluminum (Al), titanium (Ti), molybdenum (Mo), tungsten (W), gold (Au),or platinum (Pt), a compound (metal oxide or metal nitride) of the metalmaterial, or the like can be used. The thickness of the conductive filmis preferably 50 to 700 nm, more preferably 100 to 300 nm. Note that amaterial is needed to be selected which is not etched at the time ofetching the sacrificial layer. Specifically, in the case of forming thesacrificial layer using tungsten or molybdenum, the upper drivingelectrodes and the lower driving electrodes cannot be formed usingtungsten or molybdenum.

In patterning the conductive film, a method is employed in which aresist mask is formed by a photolithography method and then theconductive film is partly removed by an etching method. As an etchingmethod, a dry etching method or a wet etching method can be used. In adry etching method, an etching gas including CHF₃, ClF₃, NH₃, CF₄, orthe like can be used. Further, in a wet etching method, an etchantincluding a hydrogen peroxide solution or an etchant including bufferedhydrofluoric acid can be used.

The upper auxiliary wiring 208 is formed of the same conductive film andin the same plane as those of the upper driving electrode 206 and iselectrically connected to the upper driving electrode 206. Thus, thethickness of the upper auxiliary wiring 208 depends on that of the upperdriving electrode 206. Note that the thickness of the upper drivingelectrode 206 is preferably thin since it serves as a movable electrode.

Since the present invention employs a structure in which the upperauxiliary wirings 208 are formed only over the sacrificial layer 205(that is, the upper auxiliary wirings 208 are not formed over thestructural layer), even when the upper auxiliary wirings 208 are thin,the upper auxiliary wirings 208 can be formed without problems such asdisconnection at a step portion caused by the thickness of thesacrificial layer 205.

In addition, the auxiliary electrodes 209 are formed over the lowerauxiliary wirings 204 without forming the sacrificial layer 205.

Next, as illustrated in FIGS. 3C and 3D, a structural layer 210 isformed over the sacrificial layer 205, the upper driving electrodes 206,the upper switch electrode 207, the upper auxiliary wirings 208, and theauxiliary electrodes 209. FIG. 3D is a cross-sectional view taken alongline A-A′ in a top view of FIG. 3C.

The structural layer 210 is formed using an insulating material.Specifically, silicon, silicon oxide, silicon nitride, silicon nitrideoxide, silicon oxynitiride, or the like can be used. Note that amaterial is needed to be selected which is not etched at the time ofetching the sacrificial layer 205 in a later step. The structural layer210 can be formed by a CVD method, a sputtering method, a dropletdischarge method (typically, an inkjet method), or a spin coatingmethod. A droplet discharge method or a spin coating method can be usedwhen a starting material is an organic material. In the presentinvention, the structural layer 210 is preferably formed by a CVD methodsince the step portion generated due to the sacrificial layer 205 whichhas been formed can be rounded with the structural layer 210.

The thickness of the structural layer 210 is preferably 1 to 5 morepreferably 2 to 3 μm. A three-dimensional structure of the structurallayer 210 can be formed by removing, in a later step, the sacrificiallayer 205 which has been formed; thus, the structural layer 210 isformed over the entire surface where films have been formed. That is,the structural layer 210 is formed to cover the sacrificial layer 205,the upper driving electrodes 206, the upper switch electrode 207, andthe upper auxiliary wirings 208.

Next, as illustrated in FIGS. 4A and 4B, openings 211 are formed inpositions which are part of the structural layer 210 and overlap withthe upper auxiliary wirings 208, and openings 212 are formed inpositions which are part of the structural layer 210 and overlap withthe auxiliary electrodes 209. FIG. 4B is a cross-sectional view takenalong line A-A′ in a top view of FIG. 4A.

Next, as illustrated in FIGS. 4C and 4D, upper connection wirings 213and lower connection wirings 214 are formed over the structural layer210. FIG. 4D is a cross-sectional view taken along line A-A′ in a topview of FIG. 4C.

The upper connection wirings 213 and the lower connection wirings 214are formed by pattering the same conductive film into desired shapes.Here, as the conductive film, for example, a metal material such astantalum (Ta), aluminum (Al), titanium (Ti), molybdenum (Mo), tungsten(W), gold (Au), or platinum (Pt), a compound (metal oxide or metalnitride) of the metal material, or the like can be used. The thicknessof the conductive film is preferably 200 nm to 1 μm, more preferably 300to 600 nm. Note that a material is needed to be selected which is notetched at the time of etching the sacrificial layer 205 in a later step.

In patterning the conductive film, a method is employed in which aresist mask is formed by a photolithography method and then theconductive film is partly removed by an etching method. As an etchingmethod, a dry etching method or a wet etching method can be used. In adry etching method, an etching gas including CHF₃, ClF₃, NH₃, CF₄, orthe like can be used. Further, in a wet etching method, an etchantincluding a hydrogen peroxide solution or an etchant including bufferedhydrofluoric acid can be used.

The upper connection wirings 213 are formed so as to fill the openings211 and be electrically connected to the upper auxiliary wirings 208. Inaddition, the lower connection wirings 214 are formed so as to fill theopenings 212 and be electrically connected to the auxiliary electrodes209.

In the present invention, the structural layer 210 is formed over theentire surface where films have been formed (that is, the structurallayer 210 is formed to cover all of the sacrificial layer 205, the upperdriving electrodes 206, the upper switch electrode 207, and the upperauxiliary wirings 208), and a step is not generated by the thickness ofthe structural layer 210. Since all the upper connection wirings 213 andall the lower connection wirings 214 are formed only over the structurallayer 210, the upper connection wirings 213 and the lower connectionwirings 214 can be formed with the sufficient thickness, without beingthinned or disconnected due to a step portion.

Next, as illustrated in FIGS. 5A and 5B, openings 215 for etching thesacrificial layer 205 are formed in positions which are part of thestructural layer 210 and overlap with the sacrificial layer 205. FIG. 5Bis a cross-sectional view taken along line A-A′ in a top view of FIG.5A.

In the present invention, the structural layer 210 can have a desiredshape only by being formed over the entire surface where films have beenformed as described above; thus, in the structural layer 210, only theopenings 215 are necessary to be formed over the sacrificial layer 205by etching treatment. Therefore, only the etching selectivity betweenthe material used for forming the sacrificial layer 205 and the materialused for forming the structural layer 210 is needed to be taken intoconsideration, so that the etchant can easily be selected. In addition,because only the openings 215 are necessary to be formed in thestructural layer 210, generation of dusts in etching treatment can besuppressed to the minimum.

Next, as illustrated in FIGS. 5C and 5D, the sacrificial layer 205 isetched using the openings 215 which are formed in part of the structurallayer 210, whereby a space 216 is formed. FIG. 5D is a cross-sectionalview taken along line A-A′ in a top view of FIG. 5C.

In etching the sacrificial layer 205, a dry etching method or a wetetching method can be used. In a dry etching method, an etching gasincluding CHF₃, ClF₃, NH₃, CF₄, or the like can be used. Further, in awet etching method, an etchant including a hydrogen peroxide solution oran etchant including buffered hydrofluoric acid can be used.

For example, the lower driving electrodes 202, the lower switchelectrode 203, and the lower auxiliary wirings 204 are formed using anyof tantalum (Ta), aluminum (Al), titanium (Ti), gold (Au), or platinum(Pt); the sacrificial layer 205 is formed using tungsten (W); the upperdriving electrodes 206, the upper switch electrode 207, and the upperauxiliary wirings 208 are formed using any of tantalum (Ta), aluminum(Al), titanium (Ti), gold (Au), or platinum (Pt); and the structurallayer 210 is formed using silicon oxide. In such a case, a wet etchingmethod using a mixed solution of an ammonia solution (28 wt %) and ahydrogen peroxide solution (31 wt %) (mixing ratio=1:2) or a dry etchingmethod using a chlorine trifluoride (ClF₃) gas can be used.

When polyimide is used for the sacrificial layer 205 in the abovecombination, a wet etching method using a commercially availablepolyimide etchant or a dry etching method using oxygen plasma can beused.

Further, when silicon is used for the sacrificial layer 205 and siliconoxide is used for the structural layer 210 in the above combination, awet etching method using phosphoric acid, hydroxide such as potassiumhydroxide, sodium hydroxide, or cesium hydroxide, a tetramethylammoniumhydroxide (TMAH) solution, or the like can be used. In etching thesacrificial layer 205, a portion which is exposed to the etchant isneeded to be formed using a material which can have sufficient etchingselectivity to the sacrificial layer 205 and which is not etched evenwhen etching time of the sacrificial layer 205 is long.

In addition, by adjusting etching conditions of the sacrificial layer205, a structure (a so-called sidewall structure) may be formed in whichpart of the sacrificial layer 205 (a part 217 in FIG. 5E) is left on theside surface of the structural layer 210, as illustrated in FIG. 5E. Thethickness of the side surface of the structural layer 210 is thin, butwith the sidewall structure, the weak side surface of the structurallayer 210 can be supported.

By etching and removing the sacrificial layer 205 as described above,the space 216 is formed, so that the MEMS switch of the presentinvention can be formed.

As described above, in the MEMS switch described in Embodiment Mode 1,the upper auxiliary wirings 208 which are electrically connected to theupper driving electrodes 206 are formed over the sacrificial layer 205and connected to the upper connection wirings 213 whose thickness can berelatively freely determined, over the sacrificial layer 205. Therefore,even when the upper driving electrodes 206 are formed thinly, thinning,disconnection, and the like of the upper auxiliary wirings 208 at thestep portion generated due to the sacrificial layer 205 can beprevented. Therefore, a highly reliable MEMS switch can be formed.

A plurality of the MEMS switches described in Embodiment Mode 1 areprovided or the MEMS switch described in Embodiment Mode 1 is combinedwith a different kind of a semiconductor element such as a transistor ora diode, whereby an integrated micromachine can be formed.

This application is based on Japanese Patent Application Serial No.2007-314456 filed with Japan Patent Office on Dec. 5, 2007, the entirecontents of which are hereby incorporated by reference.

1-11. (canceled)
 12. A method for manufacturing a micromachine,comprising: forming a first conductive layer a substrate having aninsulating surface; forming a sacrificial layer over the firstconductive layer; forming a second conductive layer over the sacrificiallayer; forming a structural layer over the second conductive layer;forming a first opening in the structural layer; forming a thirdconductive layer over the structural layer, the third conductive layerbeing electrically connected to the second conductive layer through thefirst opening; forming a second opening in the structural layer; andremoving the sacrificial layer by etching using the second opening. 13.A method for manufacturing a micromachine, comprising: forming a firstconductive layer a substrate having an insulating surface; forming asacrificial layer over the first conductive layer; forming a secondconductive layer over the sacrificial layer; forming a structural layerover the second conductive layer; forming a first opening in thestructural layer; forming a third conductive layer over the structurallayer, the third conductive layer being electrically connected to thesecond conductive layer through the first opening; forming a secondopening in the structural layer; and removing totally the sacrificiallayer by etching using the second opening.
 14. A method formanufacturing a micromachine, comprising: forming a first conductivelayer a substrate having an insulating surface; forming a sacrificiallayer over the first conductive layer; forming a second conductive layerover the sacrificial layer; forming a structural layer over the secondconductive layer; forming a first opening in the structural layer;forming a third conductive layer over the structural layer, the thirdconductive layer being electrically connected to the second conductivelayer through the first opening; forming a second opening in thestructural layer; and removing partially the sacrificial layer byetching using the second opening.
 15. A method for manufacturing amicromachine according to claim 14, wherein a sidewall structure isformed in the sacrificial layer on a side surface of the structurallayer.
 16. A method for manufacturing a micromachine, comprising:forming a first conductive layer a substrate having an insulatingsurface; forming a sacrificial layer over the first conductive layer;forming a second conductive layer over the sacrificial layer; forming astructural layer by a CVD method over the second conductive layer;forming a first opening in the structural layer; forming a thirdconductive layer over the structural layer, the third conductive layerbeing electrically connected to the second conductive layer through thefirst opening; forming a second opening in the structural layer; andremoving the sacrificial layer by etching using the second opening. 17.A method for manufacturing a micromachine, comprising: forming a firstconductive layer a substrate having an insulating surface; forming asacrificial layer over the first conductive layer; forming a secondconductive layer over the sacrificial layer; forming a structural layerby a CVD method over the second conductive layer; forming a firstopening in the structural layer; forming a third conductive layer overthe structural layer, the third conductive layer being electricallyconnected to the second conductive layer through the first opening;forming a second opening in the structural layer; and removing totallythe sacrificial layer by etching using the second opening.
 18. A methodfor manufacturing a micromachine, comprising: forming a first conductivelayer a substrate having an insulating surface; forming a sacrificiallayer over the first conductive layer; forming a second conductive layerover the sacrificial layer; forming a structural layer by a CVD methodover the second conductive layer; forming a first opening in thestructural layer; forming a third conductive layer over the structurallayer, the third conductive layer being electrically connected to thesecond conductive layer through the first opening; forming a secondopening in the structural layer; and removing partially the sacrificiallayer by etching using the second opening.
 19. A method formanufacturing a micromachine according to claim 18, wherein a sidewallstructure is formed in the sacrificial layer on a side surface of thestructural layer.
 20. A method for manufacturing a micromachineaccording to claim 12, wherein the sacrificial layer is removed by wetetching or by dry etching.
 21. A method for manufacturing a micromachineaccording to claim 13, wherein the sacrificial layer is removed by wetetching or by dry etching.
 22. A method for manufacturing a micromachineaccording to claim 14, wherein the sacrificial layer is removed by wetetching or by dry etching.
 23. A method for manufacturing a micromachineaccording to claim 16, wherein the sacrificial layer is removed by wetetching or by dry etching.
 24. A method for manufacturing a micromachineaccording to claim 17, wherein the sacrificial layer is removed by wetetching or by dry etching.
 25. A method for manufacturing a micromachineaccording to claim 18, wherein the sacrificial layer is removed by wetetching or by dry etching.
 26. A method for manufacturing a micromachineaccording to claim 12, wherein the structural layer comprises silicon.27. A method for manufacturing a micromachine according to claim 13,wherein the structural layer comprises silicon.
 28. A method formanufacturing a micromachine according to claim 14, wherein thestructural layer comprises silicon.
 29. A method for manufacturing amicromachine according to claim 16, wherein the structural layercomprises silicon.
 30. A method for manufacturing a micromachineaccording to claim 17, wherein the structural layer comprises silicon.31. A method for manufacturing a micromachine according to claim 18,wherein the structural layer comprises silicon.